[VOL-1866] Changed module dependency to v12.0.0 of k8s client-go and v1.15.4 of k8s api/apimachinery in sync with other voltha components

Had to use pseudo-version corresponding to v12.0.0 of k8s client-go
because golang proxy is no longer serving the modules not complying
to Semantic Import Versioning rules including client-go v12.0.0.
Refer to https://github.com/kubernetes/client-go/issues/631 and
https://github.com/golang/go/issues/33558

Change-Id: I2e558bab7f0702f230761319eb5392a7d0532ea3
diff --git a/vendor/k8s.io/api/scheduling/v1alpha1/zz_generated.deepcopy.go b/vendor/k8s.io/api/scheduling/v1alpha1/zz_generated.deepcopy.go
index fe0c860..0392823 100644
--- a/vendor/k8s.io/api/scheduling/v1alpha1/zz_generated.deepcopy.go
+++ b/vendor/k8s.io/api/scheduling/v1alpha1/zz_generated.deepcopy.go
@@ -21,6 +21,7 @@
 package v1alpha1
 
 import (
+	v1 "k8s.io/api/core/v1"
 	runtime "k8s.io/apimachinery/pkg/runtime"
 )
 
@@ -29,6 +30,11 @@
 	*out = *in
 	out.TypeMeta = in.TypeMeta
 	in.ObjectMeta.DeepCopyInto(&out.ObjectMeta)
+	if in.PreemptionPolicy != nil {
+		in, out := &in.PreemptionPolicy, &out.PreemptionPolicy
+		*out = new(v1.PreemptionPolicy)
+		**out = **in
+	}
 	return
 }
 
@@ -54,7 +60,7 @@
 func (in *PriorityClassList) DeepCopyInto(out *PriorityClassList) {
 	*out = *in
 	out.TypeMeta = in.TypeMeta
-	out.ListMeta = in.ListMeta
+	in.ListMeta.DeepCopyInto(&out.ListMeta)
 	if in.Items != nil {
 		in, out := &in.Items, &out.Items
 		*out = make([]PriorityClass, len(*in))